The present invention relates to a laser oscillating apparatus, and in more detail, to a laser oscillating apparatus which is capable of outputting large capacity laser beams while being compact, and moreover, facilitates the attitude adjustment of the optical resonator.
In recent years, there have been various attempts to obtain a laser oscillating apparatus of small size and high output power.
As one such oscillating apparatus there may be mentioned a device in which the optical resonator is composed of a primary mirror, an output mirror, and an appropriate number of folding mirrors.
This is a device which aims at reducing the length of the lasing cavity by multiply folding the laser beam that travels back and forth between the primary mirror and the output mirror by means of the folding mirrors in the passage of the beam so as to let the laser beam pass through the lasing gas medium a number of times.
An example of such a construction is, for example, to arrange a relatively large front folding mirror at one end of the lasing gas medium, a somewhat smaller semi-transmissive output mirror in the neighborhood of the front folding mirror, and to arrange on the other end of the lasing gas medium a rear folding mirror which is parallel to the front folding mirror. In addition, in the neighborhood of the rear folding mirror there is arranged the primary mirror positioned diagonally with respect to the output mirror.
In this optical resonator, a ray of radiation which is emitted from the lasing gas medium reaches, for example, the front folding mirror on one end of the lasing gas medium after being reflected from the primary mirror on the other end and going through the lasing gas medium. Then, after being reflected from the front folding mirror, the ray travels through the lasing gas medium again, and reaches the rear folding mirror at the other end. Thereafter, the ray is reflected between the rear folding mirror and the front folding mirror for a number of times, and is arranged eventually to reach the output mirror which is placed in the neighborhood of the front folding mirror.
In this optical resonator, there are formed multiple optical paths between the front folding mirror and the rear folding mirror, obtaining an effective optical path which is several times the length of the optical resonator. This permits the realization of a laser oscillating apparatus of small size and high output power.
However, in such an optical resonator, the points of reflection of the laser beam on both folding mirrors are situated on a straight line so that the path of the laser beam becomes planar.
In this way, when the path of the laser beam lies in a plane, it is required that a portion of the plane be large enough for the passage of the path, namely, a width for the resonating cavity, and also there will be required discharge electrodes of large width for realizing a uniform discharge.
Further, when the path of the laser beam lies in a plane, the cross-section of the laser beam in resonation at each reflecting point is in a mode in which the cross-section is inverted repeatedly with a center axis that is orthogonal to the plane of reflection as the boundary. This leads to the generation of an anisotropy of the laser beam in resonation, resulting in the shape of the cross-section of the output laser beam which is flat.
Moreover, it has been customary to provide mirror attitude adjusting means of some form to the optical resonator.
However, in the prior art laser oscillating apparatus, it was frequently necessary in adjusting the attitude of the mirrors to remove the top of the laser's housing which is a gas tight enclosure. Further, the mirror attitude adjusting method is optically complicated so that the adjusting operation of mirrors consumes much labor and time.